Expansive soil swells when it absorbs moisture and shrinks when it dries out. In Denver and across the Colorado Front Range, expansive clay soil is the most significant geologic hazard in the state, and the Colorado Geological Survey reports it causes more property damage than any other natural hazard. The primary culprits are bentonite and montmorillonite clays found throughout the region.
Understanding this local soil condition is essential to keeping your foundation strong and stable.
Serving the Front Range Since 2001 | BBB A+ Rated | International Society of Micropiles Member | Lifetime Warranty | No Deposit Required
What Is Expansive Soil?
Expansive soil is clay-rich ground that changes volume with moisture. Soil expansion happens when that clay takes on water, and the more expansive clay the ground holds, the more it moves and the more force it puts on anything built above it or next to it
After more than two decades of foundation and drainage work on the Front Range, we can tell you the movement almost always traces back to one thing: changes in moisture levels in the clay. Snowmelt, irrigation, rainfall, and water shed off the house all raise the moisture in the soil, and dry spells pull it back out. The most common accelerant we find on site is poor drainage and grading that sends water straight into the clay beside a foundation. That repeated wetting and drying is what causes the damage.
The clays behind most of this movement are montmorillonite and the volcanic-ash deposits called bentonite. They run through named formations under the metro, including the Pierre Shale and the Denver Formation, both of which test as high-plasticity clay. Much of the Denver metro sits directly on or very close to them.
The force generated by soil expansion in these clays is enough to crack concrete foundations, lift slabs, and shift footings. That is how a soil condition most homeowners never see becomes a structural problem they cannot ignore.
Why Denver's Geology Makes Expansive Soils Especially Destructive
The Denver metro and Front Range sit on some of the most expansive clay formations in North America. In many areas the reactive claystone bedrock lies near the surface, right where foundations bear. Ground swelling in these clays is why homes in otherwise stable neighborhoods can develop foundation movement decades after they were built.
Closer to the foothills, we deal with a second and separate hazard: heaving bedrock. Here the expansive beds dip steeply, and because some beds swell far more than the ones beside them, they heave unevenly. That differential movement is a different mechanism from the broad swelling of flat-lying soil, and it changes what a correct repair looks like. A pier that would perform well in typical expansive soil can be the wrong call in a steeply-dipping heaving-bedrock zone, because the rock can carry the pier with it.
This is the reason we diagnose before we design. In more than two decades on the Front Range, we have learned that two homes a mile apart can sit on very different ground, and the method that stabilizes one can be wrong for the other. We read the site, the soil behavior, and the structural context first, then match the method to what the ground actually calls for. There is no one-size repair here, and any contractor who offers one has skipped the most important step.
The Impact of Expansive Soils on Your Foundation
You already know the cycle: clay swells when it takes on water and shrinks when it dries. That soil swelling and shrinking works against a foundation season after season, lifting, dropping, and shifting the structure until the damage becomes visible. It usually shows up slowly, which is why homeowners often write off the early signs as normal settling for months or years while the movement keeps compounding.
Here is what that looks like on a Front Range home.
Cracks in the Foundation
Cracking is the most common sign. Cracks can run horizontal or vertical and range from hairline fractures to wider gaps. The diagnostic ones tend to show up as diagonal cracks at door and window corners, gaps between the wall and ceiling, and stair-step cracking through brick courses. Once a crack opens, it can let water in, which worsens the structural problem and often signals a drainage issue that needs its own solution.
This is where our background matters. Because we spent years building and remodeling whole homes before we specialized, we read movement across the entire structure, not just the foundation. A symptom in the brick line, the soffits, or the roof framing can point straight back to the foundation, and it is the kind of signal a narrowly trained crew can miss.
Sinking or Settling Foundations
When the soil dries and contracts, it leaves voids beneath the foundation. Parts of the structure then settle unevenly, which pulls it out of level. That is what makes doors and windows stick, floors go uneven, and existing damage gets worse if it is left alone.
For a fuller diagnostic checklist, see our page on the symptoms of foundation damage.
Uneven or Sloped Floors
As the movement puts uneven pressure on the foundation, floors begin to slope. It affects daily comfort, but the bigger concern is what it tells you about the structure underneath.
Warning Signs Homeowners Often Overlook
The obvious cracks get noticed. It's the quieter signals that catch homeowners off guard.
The Quiet Signals
- A door that started sticking last spring and never went back to normal
- A hairline gap between the baseboard trim and the floor that widens a little each year
- A basement slab that feels slightly heaved in one corner
- Soffit distortion or a fascia line that no longer runs true across the front of the house
- A visible gap where soil is pulling away from the foundation after a dry stretch
Why These Signs Get Missed
Because the damage builds gradually, these small signals often precede major cracking by months or even years. Most of the homeowners we meet had one or two of them for a long time before a diagonal crack finally made the problem impossible to ignore. Early recognition is the most valuable thing we can give you.
What to Do If You're Seeing Them
If you're seeing any of these signs, our team serves Boulder, Denver, and the broader Front Range. Our page on the causes of foundation damage goes deeper into the mechanics behind what you're seeing.
Schedule a complimentary on-site assessment with our foundation repair team.
How to Protect Your Foundation from Expansive Soils
You can't change the soil under your home. You can control how much water reaches it, and that is where the real leverage is.
Grading and Drainage
Keeping water away from the foundation is the single most effective thing a homeowner can do. When water drains away from the house instead of pooling against it, the soil holds a steadier moisture level and moves less. Gutters, downspouts, and French drains all pull water away from the clay before it can feed the shrink-swell cycle. Our drainage and grading work is often part of the same project as foundation repair, for exactly this reason.
We almost never go to homes in Colorado that have a foundation problem and good grading. The two just seldom exist together. A practical target is roughly six inches of slope away from the foundation within the first ten feet, where the site allows for it. Fixing soil movement without also fixing the water is half a repair.
Soil Stabilization
Soil stabilization is a new-construction conversation. Before a home is built, design engineers may specify lime or cement stabilization, post-tensioned slabs, or void forms. Those are decisions made at the design stage.
For a home that is already moving, the answer is diagnosis and structural repair, not soil chemistry. Trying to alter the soil under a finished house rarely produces a reliable result, and we won't sell a homeowner an approach we don't trust to last.
Foundation Repair Solutions
If the movement has already started, there are proven ways to correct it. Our two primary methods are limited-access micropiles and helical piers. Which one we use is decided by the soil conditions and the independent engineer's design, not by installer preference.
Micropiles are drilled deep into stable bearing strata below the active expansive-soil zone. Helical piers are advanced by torquing, essentially screwed down into competent soil. In typical expansive-soil conditions, both systems carry the weight of the home past the shrink-swell layer to material that stays put through the seasons. Where the ground is more complicated, like the steeply-dipping bedrock near the foothills, the right method is whatever the site and the engineer's analysis call for. That is why we diagnose first.
We don't install push piers or resistance piers in Front Range soils. That system depends on soft soil sitting over hard rock, and Colorado's geology doesn't give us that profile. We have been called out to fix homes where another contractor's push piers kept moving for years, and we won't put a homeowner in that position.
We've never had a callback from a moving pile or pier. When we install a system, it stays where we put it. Our page on foundation repair covers the methodology in more detail.
Working with a Structural Engineer on Expansive Soil Repairs
Any serious repair in expansive soil conditions should start with an independent structural engineer's assessment. Hire an engineer directly, before calling any contractor. A stamped engineering plan makes contractor comparison honest and apples-to-apples, because everyone is bidding the same scope.
We work with and alongside independent engineers, not around them. We don't employ engineers in-house, and we think that separation is a feature, not a limitation. Our entry into foundation repair came from engineer referrals, and that relationship still shapes how we operate. Our field estimators, Tim and Lance, each bring more than 20 years of experience reading structures and scoping repairs, and our crews install engineered designs exactly as drawn, without scope substitutions.
Foundations in expansive soils have to be designed for the specific site, not off a template. Once the engineer specifies that design, our job is to build it precisely. That is the standard we hold on every project.
Frequently Asked Questions About Expansive Soils in Denver
Van Matre Construction
If your windows or doors used to open and close easily and are now tight or rubbing,you could be experiencing foundation movement.
Call Van Matre Construction for a free assessment.
